function S_i_m1 = C2I_primary(S_crtbp,u,DU,VU,t)

Tri = [cos(t),-sin(t),0;...
       sin(t),cos(t),0;...
       0,0,1];
Tridot = [-sin(t),-cos(t),0;...
       cos(t),-sin(t),0;...
       0,0,0];

Xisb   = [Tri,zeros(3);Tridot,Tri]*S_crtbp;

d = -u;
Xibp = [-d*cos(t);-d*sin(t);0;d*sin(t);-d*cos(t);0];


S_i_m1_temp     = Xisb+Xibp;

S_i_m1 = [S_i_m1_temp(1:3)*DU;S_i_m1_temp(4:6)*VU];

end